The present disclosure relates to a printing method, and more particularly, to a roller apparatus, a printing method, and a method of fabricating a liquid crystal display (LCD) device using the same, which can simplify a process and minimize a printing defect.
As an information-oriented society is developed, demands for display devices also increase. To meet the increasing demands, researches have been conducted on various flat display devices including an LCD device, a plasma display panel (PDP) and an electroluminescent display (ELD), some of which are already being widely used as display devices.
Particularly, the LCD device has advantages of good image quality, lightness, a thin profile, and low power consumption, and is quickly substituting for a cathode ray tube (CRT). The LCD device can be applied in various fields, e.g., a monitor of a notebook computer and a display panel of a television.
The LCD device includes a liquid crystal panel for displaying an image, and a driver for driving a liquid crystal panel.
The liquid crystal panel includes a liquid crystal layer between two substrates. An alignment direction of liquid crystal molecules of the liquid crystal layer is controlled by a voltage applied to respective electrodes provided on the two substrates, thereby controlling light transmittance to display an image.
The liquid crystal panel includes various patterns, e.g., a gate line, a data line, a thin film transistor, a pixel electrode, and a common electrode.
To form those patterns, a photoresist pattern can be formed by cleaning, exposure and development processes, and an etch process can be performed by using the photoresist pattern as a mask.
Since expensive exposure equipment must be used, a fabrication cost increases. Also, since a plurality of processes are performed, a fabricating process becomes complicated.
Recently, a printing method has been proposed, in which a printing pattern is formed by a printing process and a pattern is formed by using the printing pattern as a mask, instead of using a photoresist pattern.
FIGS. 1A to 1C illustrate a process of forming a printing pattern by using a related art printing method.
Referring to FIG. 1A, a roller 1 has a circular section, and is rotatable and movable in one horizontal direction. A blanket 2 with uniform thickness is disposed around a surface of the roller 1.
As the roller 1 rotates after a printing material 3 is dropped onto the blanket 2, the surface of the blanket 2 is coated with the printing material 3.
Referring to FIG. 3, a cliché 5 is provided to form a pattern from the printing material of the roller 1. The cliché 5 includes a plurality of patterns.
After the roller 1 coated with the printing material 3 contacts the cliché 5, the roller 1 rotates on the cliché 5, moving in one horizontal direction. Then, the pattern of the cliché 5 is transferred onto the roller 1, so that a printing pattern 4 corresponding to the pattern of the cliché 5 is formed from the printing material 3 of the roller 1. That is, because of the pattern of the cliché 5, a portion of the printing material 3 of the roller 1 contacting the cliché 5 attaches to the cliché 5, and the other portion of the printing material 3 that does not contact the cliché 5 remains on the roller 1.
Referring to FIG. 1C, a glass substrate 6 is provided.
After the roller 1 including the printing pattern 4 contacts the glass substrate 6, the roller 1 rotates on the glass substrate 6, moving in one horizontal direction. Accordingly, the printing pattern 4 on the roller 1 is transferred onto the glass substrate 6.
As described above, the related art printing method requires three processes of coating a roller with a printing material, forming a printing pattern onto a roller by using a cliché, and forming a printing pattern of a roller. Consequently, a process becomes complicated.
Also, if an optimum process condition is not satisfied in each process and between processes during a plurality of processes, a printing defect may occur. For example, in the case where a pattern of a cliché has a small height difference, if a roller forcibly presses the cliché, a printing material that should remain on the roller may contact the cliché and attach to the cliché. Consequently, a desired pattern may not be formed on the roller, failing to form a desired pattern on a substrate.